The invention relates to a method for the multiple access use of bit-transparent dial connections and dedicated connections in the ISDN by any subscribers and to a device for carrying out the method. Normally, in the ISDN (Integrated Services Digital Network), a dial connection is established always individually between subscribers, said connection transmitting 64 kbps also over long distances, if the subscriber so signals. At the present time, there is no possibility in ISDN to utilize the bit rate of these bit-transparent dial connections or dedicated connections simultaneously for several mutually independent voice connections. The inventive method shall make low-cost long-distance calls possible for all subscribers over the existing network owing to the fact that a trunk link can be used simultaneously by several subscribers. This leads to a reduction in connection costs. In accordance with its function, the device for carrying out this method hereinafter is named ISDN Link Sharing System (ILSS). A telephone service with advantageous fees can be realized with this ILSS device.
Functions and services of the ISDN, as well as the interfaces to dedicated lines are known and largely fixed in international standards. Furthermore, the interfaces for digital trunk groups between telephone exchanges, such as the ISDN Primary Access (PA) and the ISDN No. 7 are known. Furthermore, there is also very efficient signaling over the network between subscribers and ISDN private branch exchanges. With that, it is also possible to build up virtual private networks. Several channels can also be combined to hyperchannels, the "bit sequence integrity" being maintained. At the present time, the ISDN network interfaces, available for private facilities, are the basic access (BA) and the PA.
Numerous methods and facilities for bit rate reduction for voice and data are known, including those with statistical multiplexes for utilizing voice pauses. It is irrelevant for the invention which of these methods is used for the aimed for service.
In the private utilization of the telephone service, it is already possible at the present time in some countries that, for trunk links between regions close to one another (Local Service Area=LSA), the subscriber number of a private long-distance operator is dialed. In some cases, these operators utilize devices, which also carry out voice compression on transmission paths. Devices for bit rate reduction are also used by network operators in long-distance networks. The possibility of multiple access use of dedicated lines by means of bit rate reduction is also known for connections between private branch exchanges.
There are numerous examples of the multiple access use of dedicated lines, even for the common transmission of voice and data: patent WO91/03901, patent EP 504757 A2, cl. HO4Q-011/04. WO92/21216 is an example of the interlining of computers over the ISDN. Devices for the multiple access use of bit-transparent dedicated lines, the subscriber end points of which can be reached over switched lines from the PSTN, are also known (see, for example, ntz, volume 47 (1994), No. 11 page 791).
Furthermore, virtual private networks are realized over the ISDN and known (see "elektrisches Nachrichtenwesen", volume 64, (1990), number 1, pages 65 to 70 and "ntz", volume 47 (1994), number 11, pages 782 to 785. Subscribers, which are not subscribers of the virtual private network, can at the same time reach any long-distance subscriber.
Functions of the ISDN, used by the invention described below, are the sending of the calling subscriber number to the called subscriber (Calling Line Identification=CLI), user-specific signaling (service 1 according to ETSI) while the call is being set up and the subscriber-subscriber signaling s', all of which are transmitted in the D channel.
The possibilities of using the ISDN and digital voice compression also for dial connections between private branch exchanges is described in the Austrian patent AT 400,652 (AT30373/93). Dedicated lines between private branch exchanges, so equipped, are generally superfluous: In this last-mentioned patent application, the mode of operation of the signal converter for the bit rate reduction, for example, depends on the ISDN signaling of the remote subscriber.
With the known solutions, an independent operator of a telecommunication service cannot enable arbitrary subscribers to have multiple access use of ISDN switched lines and dedicated lines. These devices, for example, do not collect data for the billing of charges to individual subscribers and do not check the authorization. It is this in particular, however, which would be required in order to build up a cost-effective telephone service, which does not require its own trunk network. Furthermore, it is also not possible with the known solutions that arbitrary subscribers, over multiple access use of ISDN lines, can reach other subscribers directly over at a remote ISDN private branch exchange over a device for the multiple access use of bit-transparent connections, that is, without detouring over a remote ILSS device or over a local private branch exchange of a virtual private network.